A dual-mode ultra-wideband (UWB) Physical Layer (PHY) supporting single carrier and Orthogonal Frequency Division Multiplexing (OFDM) modulation can employ a common mode. The UWB PHY may be used for millimeter wave (e.g., with carrier frequency of 60 GHz) communications. The common mode is a single-carrier mode used by both single-carrier and OFDM devices for beaconing, network-control signaling, and base-rate data communications. The common mode is typically necessary for interoperability between different devices and different networks.
Millimeter-wave communications may also employ beamforming on one or more antennas in order to provide both spatial diversity and array gains. A multitude of antenna configurations such as single antenna element, sectored antennas, switched antennas, and 1-dimensional (1-D) and 2-dimensional (2-D) antenna arrays may support beamforming. Conventional beamforming, such as Eigen-beamforming, requires channel state information matrices or beamforming matrices to be fed back to the transmitting array. The Institute of Electrical and Electronics Engineers (IEEE) 802.11n standard specifies feedback information that includes row and column sizes of feedback matrices, subcarrier grouping size (e.g., cluster size), quantization bit size, and an array of actual quantized data elements starting from the lowest subcarrier index to the highest subcarrier index. For the purpose of beamforming that employs preceding matrices, the feedback information can be reduced by replacing contents of beamforming matrix with indices of a precoding-matrix codebook.
Two types of beamforming protocols are considered: an on-demand beamforming and a pro-active beamforming. On-demand beamforming may be used between two devices (DEVs) or between a piconet controller (PNC) and a device (DEV) and may occur in a channel time allocation (CTA) period allocated to the DEV for the purpose of beamforming. Pro-active beamforming may be used when the PNC is a source of data to one or multiple DEVs. This protocol may allow multiple DEVs to train their own receiver antennas for preferred reception from the PNC with a lower overhead.
Two beamforming optimality criterions are considered: a beam switching (steering) and tracking (BST) criterion suitable for all antenna configurations, and pattern estimation and tracking (PET) option for 1-D linear antenna arrays and 2-D planar antenna arrays. All DEVs that support the PET method may support the BST criterion. The PET criterion may be used only if the to DEVs that form a communication link support it. The BST is based on selecting the preferred beam from a given set of beams, whereas the PET is based on finding the preferred beam former and combiner vectors (i.e., antenna weights) that do not necessarily fail into a given set of beam directions.
Therefore, there is a need in the art for methods to efficiently achieve beamforming optimality criterions.